UV Coating Machine Principle ！

I. Overview of Core Principles

II. Detailed Explanation of Key Processes

1. Coating Process

• Purpose: To uniformly and continuously apply UV coating onto the surface of substrates (such as paper, plastic, metal, wood, etc.) to form a wet film of a certain thickness.
• Common Coating Methods:
  • Roller coating: The coating is transferred to the substrate surface through contact between the coating roller and the substrate. It is suitable for flat substrates and allows control of the coating thickness.
  • Knife coating: The gap between the knife and the substrate is used to control the amount of coating. It is applicable for high-viscosity coatings or scenarios requiring precise thickness.
  • Spray coating: The coating is atomized through a nozzle and sprayed onto the substrate surface, suitable for complex shapes or large-area substrates.
  • Curtain coating: The coating forms a uniform "liquid curtain" through a flow channel, and the substrate passes under the curtain to complete the coating, which is efficient and ensures uniform coating.

2. UV Curing Process

• Core Reaction: After absorbing UV light of specific wavelengths (usually 200-400nm), the photoinitiators in the UV coating decompose to generate free radicals or cations, triggering polymerization reactions in resins (such as acrylates), which rapidly transform from liquid to solid cross-linked films.
• UV Light Sources: High-pressure mercury lamps, metal halide lamps, LED UV lamps, etc., are commonly used. Among them, LED UV lamps are gradually becoming mainstream due to their low energy consumption, long service life, and single wavelength (which can match specific photoinitiators).
• Curing Characteristics: The curing speed is extremely fast (usually completed within a few seconds), with low energy consumption, no volatile organic compound (VOC) emissions (environmental protection), and the cured coating has stable performance.

III. Basic Structure of the Equipment

1. Unwinding device: Used to place the roll of substrate to be processed, ensuring the substrate enters the coating system smoothly.
2. Coating system: Includes coating rollers, scrapers, coating tanks, etc., responsible for evenly applying the coating onto the substrate surface.
3. Drying/pre-curing device (in some models): For UV coatings containing a small amount of solvent, low-temperature drying is first used to remove the solvent to avoid bubbles during curing.
4. UV curing device: The core part, including UV lamps, reflectors, cooling systems (to prevent substrate deformation due to high temperature), etc.
5. Winding device: Re-winds the cured substrate into a roll to complete the processing.
6. Control system: Uses PLC and other control equipment to adjust parameters such as coating speed, coating thickness, and UV lamp power to ensure stable operation.

IV. Application Advantages

• Efficiency: Fast curing speed enables continuous production and improves productivity.
• Environmental protection: UV coatings have no VOC emissions, meeting environmental requirements.
• Excellent performance: The cured coating has high hardness, strong adhesion, wear resistance, chemical corrosion resistance, and controllable gloss (can achieve high-gloss, matte, etc., effects).
• Wide applicability: Can handle various substrates, including paper, plastic, metal, glass, etc.